G protein-coupled receptor (GPCR) is a seven-transmembrane receptor and has a function of transmitting signals from hormones, neurotransmitters, cytokines or other molecules to cell membranes. Human GPR30 (hGPR30) known as one GPCR (Owman, C. et al., Biochem. Biophys. Res. Commun., 228, 285-292, 1996) is reported as follows.
When human umbilical vein endothelial cells are exposed to shear stress, the expression amount of hGPR30 is increased (Takada et al., Biochem. Biophys. Res. Commun. 240, 734-741, 1997). The expression of rat GPR30 (also referred to rGPR30 or GPR41) in myocardial cells is induced when the rat GPR30 is exposed to low oxygen stimulation and then returned to the usual medium (Kimura et al., J. Biol. Chem., 276, 26453-26460, 2001).
hGPR30 is expressed in breast cancer tissues, breast cancer derived cell lines, and placenta on which estrogen receptor (ER) is expressed (Carmeci, C. et al., Genomics, 45, 607-617, 1997). When breast cancer derived cell MCF7 is stimulated with progestin in the presence of estrogen, the expression amount of GPR30 is increased (Ahola, T. M. et al., Eur. J. Biochem., 269, 2485-2490, 2002). Sex hormone is known as adjusting many reproductive functions. For example, in the uterus, progesterone inhibits the proliferation of endometrial epithelial cells induced by estrogen. By contrast, the function of progesterone in mammary gland is not much clarified. Progestin inhibits the proliferation of breast cancer cells and normal mammary gland epithelial cells. It has been shown by an experiment using antisense RNA that the inhibition on proliferation of MCF7 cells by progestin is caused by an increase of the expression amount of GPR30, and thus the possibility that GPR30 is involved in suppressing the proliferation of breast cancer derived cells has been shown (Ahola, T. M. et al., Endocrinology, 143, 3376-3384, 2002). It has also been shown that the inhibition by progestin and GPR30 on proliferation of breast cancer derived cells is caused by the inhibition on activation of MAPK (mitogen-activated protein kinase) (Ahola, T. M. et al., Endocrinology, 143, 4620-4626, 2002). Activation of MAPK by estrogen mediated by GPR30 in breast cancer derived cells such as MCF7 or the like has also been reported (Filard, E. J. et al., Mol. Endocrinol., 14, 1469-1660, 2000). It has been suggested that this occurs because membrane binding EGF (epidermal growth factor) existing on the cell surface of the breast cancer derived cells such as MCF7 is solubilized by the activation of GPR30, and thus the EGF receptor is activated (Filard, E. J. et al., Mol. Endocrinol., 14, 1469-1660, 2000). By contrast, it has also been suggested that stimulation by estrogen increases the intracellular cAMP concentration mediated by GPR30, and thus Raf is suppressed by RKA (protein kinase A) activation to reduce the activation of MAPK (Filard, E. J. et al., Mol. Endocrinol., 16, 70-84, 2002). These facts indicate that GPR30 is a cell membrane receptor of estrogen, and a pharmacological analysis on this issue has recently been reported (Thomas, T. et al., Endocrinology, 146, 624-632, 2005).
Tacrine (1,2,3,4-tetrahydro-9-acridinamine) is an acetylcholine esterase inhibiting substance and is used as a therapeutic agent for Alzheimer's disease, but has not been reported as acting on an intranuclear receptor of estrogen.